Coordination circuit



J. MILLMAN 2,605,408

COORDINATION CIRCUIT 2 SHEETSSHEET 2 I I 1 I1 1 H1 H HM wwHuh l H 51 AH ll Illl. llllllill July 29, 1952 Filed Jan. 15, 1946 synchronizing on timing f signal.

Patented July 29, 1952 COORDINATION c eam Jacob Millmani Brookline, Mass; "assignor; by

- mesne assignments, to the 1 United States of America as represented by the Secretaryof the Navy a J Application Jan ry 15, 194s,v Serial mi 541,335

This'invention relates to electric synohronizers and more particularly to a circuit for deriving "an electric pulse of a relatively low repetition rate from a high-periodicity re'current pulse signal and. for timing each low repetition rate pulse to'coincide with a pulse of the higher repetition rate.

The multivibrator is commonly employed as a timing device wherein the signal output of the niultivibrator is of a repetition rate which is a sub-multiple of the repetition rate of anin'put Inherently, therefore. the multivibrator is limited; in its function as a timer or frequency divider to applications involving integral'repetition rates. Y

The. present invention overcomes this limitation and provides a circuit for generating an electric pulse signal of a, relatively low repetition rate that is non-integral with a pulse of higher repetition rate from which itis derived.

An object of this invention is to provide a circuit which acts as a frequency divider and derives an electric pulse of anon-integral'and'relatively low repetition rate from a pulse of a higher v repetition rate.

Another object is to provide a, circuit for'synchronizing each pulse of a signal of a relatively low average repetition rate to a pulse of a signal of a relatively high and non-integral repetition rate.

A further object is torprovide-a synchroniaer in which a control signal ofrelatively low frequency is combined with a pulse signal of a high and non-integral repetition rate so that there is a resultant output pulse signal having an average" repetition rate equal to the control frequency and each pulse of which is synchronous with a pulse of the higher'repetition rate signal.

These andv other objects and featuresof this invention will become apparent upon a consideration'of the following detailed description when taken together with'the accompanying drawings, the figures of which illustrate atypical embodiment of this invention.

' Fig. 1 is a'block diagram of a radar system and a cooperating recognition system together with a system for coordinating their operation, including a synchronizer or frequency divider according to this invention; and

Fig. 2 illustrates the wave forms at variousan A-scope indicator type of presentation on which the radar'output gives a'positive deflection, theposition of the deflection along the-base line being proportional to range. Recognition signals are also displayed on the A-scope with a negative deflection on 'horizontal sweepwhich is vertically displaced from the radar sweep so "thatconfusion-isavoided. The recognition systern includes an interrogating transmitter and a receiver for reception of recognition signals from f e dl ar e s n Pm fi lli l the interrogating signals; The antenna beam of therecognitionsystem is' broadenthan thaii'of 'the'radarisystem. To provide the necessary'idi- "rectivi tyj for the recognition antenna and un- 7 mu nsigna'ls, the recognition antenna beamls mistakable association of radar target and recogl'oloe switched, the echoes returned 'for'each q'fthe "two lobes being horizontally displaced on the LA- scope and their amplitudes matched'as an index of the centeringof the beam on the targetunder which the first recognition e'cho appears.

this illustrative embodiment of the invention, the horizontal sweeps for the A- scope are ,gerieratedby the radar system; operating at a repetitioni'ffrequencyof 890 pulses per second.

. The, recognition system operates from; a source of 60 cycle current, has a .1 0? fswitching frequency of 60" cycles and interrogates; therefore,

at a rate of 120 pulses per second; 'Ihefs'ynchronize'r of, thisinvention is the heart of the coordination. 'system and' utilizes a full-wave rectified 60 cycle wave .or' a 1210 cycle control frequency,

' during each cycle of which onextrigger out of the series of'radar nodulator pulses is selectedto trigger the interrogator. Simultaneously; f the other units of the coordinating system provide blanking for the radar receiver, .unblankingfof the cogn ti n r eiver; an r i l di la 3 ment of the horizontal sweep on the A scopein 'f rom that {of "the radar systemg Also on alterordr. 1 1 apart h reco n t on, s gi' ec "nate' interrogator pulses, "the" heaps sweepfis j displaced horizontally so that the signal: return from each lobe of the recognition system antenna, beam rnay beseen separately for matching' of amplitudes 1 H Y Referring to Figs. 1 and 2, radar system lllincludes the conventional units, atransmitter with pulse modulator, receiver, antenna," horizontal ray tube indicator l l.

sweep generator, and the A scope type cathode I From terminal 12; the modulator of radar system l0 supplie a series of negative triggers [6 to unit ll, comprising. in-

verterand cathode follower stages. Pos'itive trigger 18 are produced at the outputof unit Iland supplied to synchronizer unit I9. Synchronizer I9 receives triggers I8 which are the high-periodicity recurrent pulse signal input derived from radar system ID, at a first input circuit connected to terminal I4. The signal at terminal I4 will be referred to hereafter as the "input signal. The multivibratorofnnit 20 is a conventional-two-rtoone dividercompleting. one cycle and starting another of square wave 2I when triggered by every other pulse of output I8. Square wave 2| is dif-L ferentiated by capacitor 22 and resistor 23 in series to ground and the resultant output 2 t with alternate positive and negativeptriggers appears at terminal 21. From terminahf2'l;..t zi gers.z26

are supplied to selector 25::and:.also:.imunitflll:

means for-combining the input signal. and the.

: .ficontrolsignal" and for repeating.ortranslating '1 onlya -p0-rtion -f..the combined signals. It yvill -bedescribed. in greater .detail hereinafter; ,but ...-briefly,; it. includes. a :pentode having. wave .34gap- (plied .-.itsscr.een:. grid. and triggers 26 @applied;

itoi s eon ml .grid. Theoutput; is takenfrom the .ecathode..circuitand...reproduces .only those ..-f ew po'sitive. triggers 1 otwave. ZI-iv which-occur. .during each.. cycle :of-rwavel3 i. when.. the screen ..grid of put of selector .25. is wave fll,..whose..first.trigger .,.during .each cycle of. wave. 34- ,is selected to trig- .s-gerfia pulseeresponsive. .means comprising multiv ibrator.38. The square wave .output 39. of multiayibratone38 .isarecurrentepu1se.,signal.. which. is;

gdifferentiated bycapacitor l I1 and. resistor .4 Icon- -mectedin'series-to ground, waveM appearing at gtheirjunction with. alternatelypositive and nag- .ati-ve triggers. .Multivibrator. .46 ,is triggeredv by v .ithe po'sitive tri gersto'nly of wave 42..and gener- 'ates...square..wave 41. .Square wave' 4'! .is applied ..,to;i;he,control grid 7 of. the pentode. of .selector '48 faiid positive tri gers' .I 8- areapplied .to the screen .g rid-..ofr.the pent0.de .of selector .48. through .cougplingcondenser...I-Il4. The, resultant output negaf. .tivetriggers.i49..are .appliedto 50, comprising .1 inverter and. cathode .follower stages-,-. whose out- ,.put. is..=wa.vel.5 I. Each. pulse.of .wave. 5 I- triggers v.... rrn'iltiyibrator 52, generating-square.. wave 53.

l Square 'wave 41,. trigger :wave 5 I, and .square ,jl flvejiialso constitute blanking .and .unblanking .=gates-and.triggers for coordinating th operation 'ofrecognition; system .60 with radar system -I 0. Recognition system .60 includes anlinterrogating Qltransmi-tter, a receiver for. reply signals. from he .tube of selector. 2-5 .is also positive. The. out-.-

nate sweep traces of the recognition display on A-scope II. Positive trigger 5| i applied to terminal 63 to trigger the interrogating transmitter. Square wave 53 is applied to terminal 64 to un- 5 blank the receiver for reply signals from equipment responding to the interrogator. The dotted line between antenna 6 I: and "60 cycle A. C. source 29.indicat es.;that source 29 controls the 60 cycle lobe switching of the antenna beam.

Returning to multivibrator 28, it is triggered by the positive triggers of wave 21 and supplies a --negai',-ive"gate I0 to the control grid of the pentode of-selector I I 'whose'constitution is similar to that ..;of.se1e.c.t0r: 48. Positive triggers I8 are supplied :15:=-. o.-the :screemgrid of the pentode of selector II,

whose output' wave I2 triggers unit 15, comprising multivibrator and cathode follower stages, supplying square wave 16 to terminal I! of radar .system 210 to blank the radar system oif'when 2.0 recognition system filltis operating. On the face ,.of.A-scope I I .asshownin Fig. 1, -'I8-.is the. radar ...tracea.and- I9. is the, recognition trace. ,Bositiye .epipufill. is the echoofa targetresponding to,; in-

,terrogation. The negative pips 8 I. and.82.are the ...amp1itude. matchedpips of. the recognitiopsig- -nals. in eachlobe of the recognition antenna systern 6 I, with the first pip 8| coming directly under the target 80 whichit identifies.

. Selector 25 comprises pentode tube 90, a source of plate potential connected at terminal 9I screen I resistor 92, connected. at oneend to ground, cathode. resistor 93,similarly connected .to ground, and asource ofpositive-cathode biasconnected atterininalf94.andcoupledthrough resistor 9 5 to,the g cathode. 1 .Terminal 2! .ties'ftothejcontrol, gridf-of tube .90. ."The1120 cycle .wave .32 is coupledtothe screen gridjof tube .90 throu h .Cf pacitor 33. The .outputfrom selector 25 is taken from .th elcathode of. tubeiflll. to. trigger. multivibrator 38. Selector 0 '48 comprises pentodetube-.l00,.plate reSistorIIJI coupling the .plate. to asourceofplatepotential connected .at terminal 102, screen resistor I03 coupling the .screen. to the ground, capacitor 104 coupling. wave I8 to the screengrid, capacitor I05 coupling the output of multivibrat,or-;46;to the control grid, and grid leak-resistor I06 connected ..,between controlgrid andground. Thecathode ,..of...tube.IOIl.-is grounded :and output wave 49 is Itaken fromitsplate.

50 In Fig. 2 are shown the wave forms at various ..points of thecircuitof Fig. 1 in'their proper. time relationships... By reference to these; waveforms and. the circuit .of Fig. l, the operation-10f ;the

. system for coordinating. the radar and-recogni- .tionsystemswill be readilyunderstood.

,Themodulator of radar system Iosuppliesa negative triggenwave It .-with;- a repetition-irequency of 800 perasecond. .-.This-trigger .l61is'syn- .chrono,us-with the pulsing 'ofjthe", radar. transmitter and. the start .of. eachhorizontal-sweepof A-scope- II.- Fromytrigger Iii-is to beqderivedffl-by synchronizer .I 9,. the, trigger. 15 I for pulsing-Lthe interrogating transmitter of. ;recogni-tion; system 60 at a repetition frequencysof.120-;per;second.

55 The individualtriggers of the .waveflB. are numberedfrom I- to- .I 4 for. fixing. time: relationships :of. the chainof wave forms .in the circuit of-Fig. 1. Unit I1 takes each negative trigger I 6 -from ;the modulator and inverts it-to supply positive {trigger .70 I8 to multivibrator 20. .-E'ach.trailing edge of square. wave 2| is coincident withan odclnumbered trigger of wave I8, starting with trigger I. The constants of multivibrator 20 are such;,that .the leading. edges of square. wave 2 I reach; pre- ..75 code. .the. even-numbered: triggers of --wave I8.

Square wave 2 I" is differentiated by capacitor 22 and 'resistor 23 to produce trigger wave '26} hav-'- 7 ing nega'gtive} triggers coincident-with the odd because" the control grid is ne'g'ative wlienthey appear o n the screen grid and hencepnly odd numbered triggers appear'in output wave I2;

Block istriggered'by each pulse of wave m, generating square wave 16 whose positive gate 7 unblanks the receiver of radar system 10. Thus,

the radar display appears onfA-scope I l following odd numbered triggers of'wave l8 and at a repetition rate of 400 cycles. V I

'-The even numbered triggers of wave l8 are reserved for triggering recognition system 39 ac'- cording to the control frequency'of 60 cycle A. C. source 29 Rectified 60 cycle wave 32 has its D'L' 'G. component removed by capacitor 33 as shown by wave 34, {where the dashed lineis the D. C. level. Wave 34 is applied to the screen grid of pentode'illl of selector whose nontrlol gridreceiveswave 26.- "*Pentode QQl'is-biase to cut ofifaridconductsonly when the control n'd screen grids are driven positive "simmtanjeousiy. Output wave 31 of selector 25 corresponds to all even numbered pulses of Wave l8, since the positive pulses of wave 26 are all even numbered. It will be noted that each trigger of wave 3'! precedes the corresponding trigger of Wave I8 by the amount established by multivibrator 20 in generating square Wave 2|. Also, for each half cycle of the 60 cycle supply, or each cycle of wave 34, there are either one or two triggers in wave 3]. Unit 36 is a multivibrator which, is triggered by the first'trigger of wave 31 that appears at its inputlto initiate a'pulse of a recurrent-pulse signal', square wave 39. Thepositive gate orwidth of the resulting square wave; 39 is adjusted to er;- tend beyond the next trigger "of 31 if there. should be. a second one in any cycle of wave 34, asjslio'fwn.

Thusmultivibrator 38 is rendered unresponsiyeto all but the selected first appearing trigger ofwave 31. Square wave 39 after differentiation "by capacitor 40 and resistor 4! becomes trigger Wave 42. Multivibrator 46 responds only to the positive pulses of wave 42 and its output square wave 4! has a positive gate which is centered about one even numbered trigger of wave l8 for each cycle of 120 cycle wave 34.

Selector 48 contains another selector pentode I00 which is biased to cut-off. Square wave 41 is fed to its control grid and triggers l8 to its screen grid. Only a trigger of wave H! which occurs during the positive gate of square wave 41 will result in an output from pentode H30, as shown in wave 49, and this output will correspond in time to one even numbered trigger of wave [8 during each cycle of 120 cycle control wave 34. Thus a trigger 5! is provided for the interrogating transmitter of recognition system an by inverting trigger 49 in unit 50. I

The derivation of trigger 5| from trigger [8 demonstrates how this invention provides for the derivation of an electric pulse of a low repetition rate from a pulse of a high repetition rate. It will be noted also that although triggers 5| and I8 are of non-integral repetition frequencies,

each i 'rj r-s l -coincides with a; trigger rthe higher repetition" rate trigger "18' and, in -"tl'1is sense, synchronism is achieved; i

- Simultaneously with the triggering of the interrogator of recognition system 6 0, trigger 5i triggers' multivibrator 52 to generate square wave 53 which is applied to terminal 64 of recognition system 6|; to provide an unblanking' gate for-its interrogator receiver. To provide the lobe switching displacement of the horizontal recognition trace onthe A scope H,,s quare wave 41 is supplied to multivibrator 68 which generates a gate 69, havinghalf the repetition frequenoy'of wave 4! and occur ri.ng;at every otherpulse of inter rogator trigger-5l.- By theterm gate as'used in this' specification is meant a voltage pulse used for gating or otherwise controlling thejoperatiori of a succeeding circuit. By applying this gate 68 to the cathode of the tube supplying the sweep of A-scope ll, alternate sweeps for the recognitiontrace are displaced horizontally, which is the desired presentation for lobe matching. 7

The resultant presentation on the face of A- scope I] was described in connection with Fig. 1'.

Itwill be noted that in'addition to its primary function in this invention as a deriver of a pulse of low repetition frequency from apulse of higher repetition frequency, synchronizer i9 provides gates and triggers for other functions in coordinating the operation of' radar system lfl and recognition system 60. For example, multivibrator 20 is employed as a] two-to-one divider to provide, among other things, for radar and recognition system sharing of A-scope ll presentation on alternatextriggers'of wave I8. However, it is readily apparent'that multivibrator 20, capacitor 22, and'resistor 23 are not essential to this invention since triggers It could. be applied directly;toselector 'Zi Further more, the repetition rates ofjsquare'wave 39, square wave 41 and trigger 5] are the same so that square wave 39 could bedirectl lltilized asthe derived low frequencysignalaccording to this invention, the synchronizer then being further simplified by the elimination of capacitor 40, vresistor 4i, .multi vibrator 46, and selector .48. i

From the foregoing description; .it will be readily seen that this invention provides a circuit for deriving an electric pulse signal of nongintegral and relatively lowrepetition rate from a pulse signal of .a higher repetition rate. I Although there is shown and described only a certain' specific embodiment of this invention in-a coordination system, the many modifications possible thereof will be apparent to those skilled in the art. Therefore, this invention is not to be limited except insofar as is necessitated by the prior art and the spirit of the appended claims.

What is claimed is:

l. A frequency divider comprising, a source of voltage pulses having a constant repetition rate, an alternating current power source, a rectifier for deriving a unidirectional cyclic con- I trol voltage from said alternating current power source, a vacuum tube selector circuit respon-V Z sive to pulses from said source and to said cyclic control voltage to repeat during each cycle of pulses repeated idurirrg an immediately ;,subse+ guent interval equal to asubstantial,portion; of the period of said control voltage. v

2. Aifrequency divider comprisin arsourcei of voltage trigger pulses of constant repetition irequency, means responsive ;to trigger pulses irom said source .to produce .two series .of voltage pulses, .thefirst of-saidseries of pulses occurring in time coincidence with odd numbered trigger pulses from said-source, the second of said series responsive to the second of said series of pulses and to said control voltage .to .repeatduring each cycle of said control voltage a limitednumber of pulses fromsaid second series .of pulses, a multivibrator responsive tothe first ,of said repeated pulses to produce a positivesquare wave output voltagehaving time duration including subsequent pulses repeated by said selector circuit, a derivative circuit responsive to the 'output square wave of said multivibratorto produce a single positive voltage pulse for each cycle of said .control voltage preceding by said 'predetermined'ti'me interval an even numbered trigger pulse from said source, a second multivibrator responsive .to positive pulses of .said derivativecircuit to produce an output square, wave having apositive portion .of double said predeterminedtime interval,. and a second selector. circuit responsive to trigger pulses from said source andthe output square wave of said secondmultivibrator to produce-one output pulse in time ,coincidence with evenjnumbered trigger pulse from said source during eachcycle of said'control voltage.

'3. A circuit for coordinating. and synchronizing the operation of the components of .a {combined microwave radar search system and .a radio recognition system comprising, a source ,of repetitive trigger voltage pulses, ;a frequency divider responsive to pulses from said source for producing an output square wave having positive portions of longer time duration than the negative Qportions, a derivativecircuit responsive to the out put of said frequency divider'forproducing negativefvoltage pulses in 'timecoincildence with ,odd

numbered pulses from said source and positive voltage pulsespreceding in time by a predetermined interval the even numbered pulses from said source, a source of alternating current power, a rectifier responsive 'tovoltage from said 18 alternating current "powersource to produce 113 unidirectional cyclic control voltage wave, ;a vacuum tubeselector circuit responsive to. positive pulses .from said derivative. circuit and-to said control voltage wave to produce output pulses preceding by said predetermined time interval an even pulse from said source of trigger voltage pulses and coincident with a :cycle of said control voltage, a multivibrator responsive to the first coincident pulse from said selector circuit to .generate an output square wave having-a time duration includingsubsequent-pulses fromsaid selector circuit coincident with the cycle of said control voltage,a second derivative circuit responsive to the output of said multivibrator to produce 'asin'gle positive pulse m time coincidence with each cycle of said. control voltage wave and preceding by said time interval even pulses from said source of trigger voltage pulses, a second multivibrator responsiveto positive pulses from said second derivative circuit to produce a square wave having a positivepor ,tion of double said predetermined time interval from said source to reject odd numbered pulses iron said source and to produce one output pulse in time coincidence with an even numberedpulse from said; source during each cycle of said con trol voltage. JACOB MILLMAN.

REFERENCES CITED The followingsreferences .are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,132,655 Smith Oct. 11, 1938 2,145,332 Bedford Jan. 31, 1939 2,171,536 Bingley Sept. 5, 1939 2,212,558 Blumlein Aug. 27, 1940 2,270,773 Sonnenta'g Jan. 20, 19.42 2,338,395 Bartelink Jan. 4, 1944 2,406,019 Labin Aug. 20, 1946 2,462,100 Hollabaugh Feb. 22, 1949 2,462,265 Hirsch Feb. 22,1949 2,519,763 Hoglund Aug. 22, 1950 FOREIGN PATENTS Number Country Date 510,881 Great Britain Aug. 8,.1939 

